Report (4) GEOPACIFIC
Real-World Geotechnical Solutions
Investigation • Design • Construction Support
September 3, 2020
GeoPacific Project No. 15-4010
Riverside Homes, LLC
17933 NW Evergreen Parkway, Suite 370
Beaverton, OR 97006
Via email to Amo Avgi (aavgi(a7riversidehome.com)
Subject: GEOTECHNICAL OBSERVATION OF FOUNDATION SUBGRADE
ELDERBERRY RIDGE SUBDIVISION—LOT 17
TIGARD, OREGON
GeoPacific Engineering, Inc. (GeoPacific) conducted on-call density testing and construction
observation services for the Elderberry Ridge Subdivision site. This letter addresses the footing
subgrade conditions at Lot 17. It is our understanding that the planned structure will consist of a
single-family daylight basement residence utilizing conventional spread footings.
GeoPacific personnel visited the site today to observe subgrade soils following the foundation
excavation for Lot 17. At the time of our arrival, the excavation was complete and extended
approximately 12 to 48 inches below the surrounding grade. The foundation bearing material
consisted of engineered fill soils over most of the excavation. The foundation subgrade soils
were evaluated with a hand probe and determined to be very stiff consistency throughout the
excavation. The footing layout of Lot 17 and the adjacent lots is stepped on a 3H:1V slope.
Footing-to-slope setbacks were evaluated and determined to be adequate due to the rear
footings being at the base of the slope. Footing-to-wall setbacks are not an issue.
Based on observed conditions, the footing subgrade soils are considered suitable for foundation
support. The foundation subgrade as prepared is considered suitable to support the planned
allowable bearing pressure of 1,500 psf. Estimated settlement under the allowable bearing
pressure is 1 inch total, and 1/2-inch differential, measured over a horizontal distance of 20 feet.
Care should be taken to avoid saturation or disturbance of footing subgrade soils during and
after excavation. If footing bearing soils become saturated or disturbed, any softened soil or
slough should be removed and replaced with crushed aggregate or additional concrete. In
general, footing excavations should be cleaned such that no more than approximately %-inch of
loose soils are present prior to pouring concrete.
Construction should include typical measures for controlling subsurface water beneath the
homes, including positive crawlspace drainage to an adequate low point drain exiting the
foundation, visqueen covering the exposed ground in the crawlspace, and crawlspace
ventilation (foundation vents). The homebuyers should be informed and educated that some
14835 SW 72"d Avenue Tel (503) 598-8445
Portland, Oregon 97224 Fax(503)941-9281
Elderberry Ridge - Lot 17
GeoPacific Project No. 15-4010
slow flowing water in the crawlspaces is considered normal and not necessarily detrimental to
the home given these other design elements are incorporated into its construction. Appropriate
design professionals should be consulted regarding crawlspace ventilation, building material
selection and mold prevention issues, which are outside GeoPacific's area of expertise.
We have prepared this report for Riverside Homes, and it should not be relied upon by third
parties without consulting GeoPacific. Within the limitations of scope, schedule and budget,
GeoPacific attempted to execute these services in accordance with generally accepted
professional principles and practices in the fields of geotechnical engineering and engineering
geology at the time the report was prepared. The conclusions and interpretations presented in
this report should not be construed as a warranty of the subsurface conditions.
No warranty, expressed or implied, is made. The scope of our work did not include flood hazard
evaluations, environmental assessments, the presence or absence of wetlands; or potential
hazardous substances in the soil, surface water, or groundwater at this site.
We appreciate this opportunity to be of service.
Sincerely,
GEOPACIFIC ENGINEERING, INC.
C / 14
OREGO,
EXPIRES:06/30/2 21
James D. Imbrie, G.E., C.E.G.
Principal Geotechnical Engineer
2 GEOPACIFIC ENGINEERING, INC.
i
FOUNDATION CERTIFICATION
SETBACK
FR� 15 RE� IFEET LOT 17 OF "ELDERBERRY RIDGE"
FRONT GARAGE: 20 FEET WASHINGTON COUNTY, OREGON
SIDE: 5 FEET
REAR: 15 FEET DATE: SEPTEMBER 3, 2020
SW 76TH AVE % 'TRACT F'
X8/8'52'40*E
L=28.58' 23.51'
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---+ t 1 SCALE 1" = 20 FEET
— ----5.00' ,
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---I- --1 r / -- 6.0'
z s.o -- LOT 18
w o I, CLINTON H. STUBBS JR., A REGISTERED
0.
a LOT 17 3 PROFESSIONAL LAND SURVEYOR IN THE STATE
W I N OF OREGON, HEREBY CERTIFY THAT I HAVE
N< b i s ACCURATELY SURVEYED AND MAPPED THE
'- r. 5 FOUNDATION FOR LOT 17 OF "ELDERBERRY
vai c "' RIDGE", AS STAKED ON SEPTEMBER 3, 2020.
z Ai
THE BOUNDARY UNES DEPICTED HEREON WERE
___-_ ' ESTABLISHED BY HOLDING RECORD INFORMATION
I LOT 1 fi 1 AND MONUMENTAT1ON FROM THE PLAT OF SAID
SUBDIVISION, THIS CERTIFICATION SHOULD NOT
- - -
SERVE AS A BOUNDARY SURVEY.
______
----- r 23.4 1 \--SETBACK LINE______- - -J ' (TYPICAL) REGISTERED
i 1 PROFESSIONAL
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N88'52'40'W LAND SURVEYOR
3W 50.00' °%
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'TRACT E'
CO , if i
JANUARY 15,N2 2
CLINTON H. STUBBS JR.
3 I 55469LS
(i) RENEWS: 06/30/22
PREPARED FOR: JOB NAME: ELDERBERRY RIDGE
JOB NUMBER: 1884 IN ORTHWEST 1815 NW 169th PLACE,
RIVERSIDE HOMES, LLC. SUITE 2090
17933 NW EVERGREEN PLACE DRAWING NUMBER: 1884 STAKED EAV ERTON, OR 97006
SUITE 370
BEAVERTON, OR 97006 DRAWN BY: BJA 0 URVEYING AX:503-848-2179
Inc.. nwsurveying®nwsrvy.com
CHECKED BY: CHS